System for the determination, the evaluation and the control of the refractive and accommodative status of the eye

ABSTRACT

The system for the determination, the evaluation and the control of the refractive and accommodative status of the eye according to the present invention includes: 
     a scanner (AN) to be placed before the eye optically corrected or not, and completely or partially consisting of material polarizing the optical radiation, and divided into two parts with perpendicular polarization and; 
     an illuminated target (MR), completely or partially consisting of parts out of polarizing material, having the polarizing axis parallel or perpendicular to each other, whereby said target may comprise means for moving said parts and for rotating said target onto the longitudinal axis.

The present invention concerns a system for the determination, theevaluation and the voluntary control of the refractive and accommodativestatus of the eye. The system includes a scanner, completely orpartially consisting of material having the capacity of polarizing theoptical radiations, and a target consisting completely or partially ofmaterial having the same polarizing capacities. The uneasiness sometimeslinked to the accommodation, i.e. to the power increase of the optic eyesystem, mainly due to the shape variation of the crystalline lens, iswell known, as well as the need of evaluating the exerted accommodationand its entity.

Also the need of evaluating the kind and the entity of the refractiveerror or ametropia is known, i.e. the surplus or lack of power of theeye, such as not to allow--in conditions of not exertedaccommodation--the correct focusing on the retina of the image of atarget placed at the optical infinity.

A power surplus determines the formation of the image before the retina(myopia), a lack of power determines the formation of the image beyondthe retina (hypermetropia), a difference of power between the twomeridians of the optic system causes the formation of two images in theshape of segments perpendicular to each other (astigmatism).

The main aim of the present invention is allowing the evaluation of thekind and entity of refractive error of the eye, the measuring of theexerted accommodation, the voluntary control of the accommodation and ofthe reduction or the solution of psychophysical uneasiness and theconsequences thereof connected to accommodation.

The aim set forth is reached by means of the system for thedetermination and control of the refractive and accommodative status ofthe eye according to the present invention, consisting of:

a scanner, through which a target is examined, with the eye opticallycorrected or not, and completely or partially consisting of materialpolarizing the optical radiation, and divided into two parts withpolarization axis perpendicular or nearly perpendicular to each other.The visual axis of the eye to be examined passes near the separationline between the two polarized half-fields or through the same;

a target, completely or partially consisting of parts out of materialpolarizing the optical radiation, having the polarizing axis parallel ornearly parallel, perpendicular or nearly perpendicular to each other,possibly including means for moving the parts and possibly means forrotating all or a part of the target onto the longitudinal axis, so thatas the scanner and the target lie on front-parallel planes or on nearlyfront-parallel planes, and as the scanner is placed, with respect to thetarget, in such a way that the polarizing axis of the polarized parts ofthe target is as parallel and/or perpendicular as possible to thepolarization axis of each of the polarized parts of the scanner, onlythe optical radiation, coming from the non-polarized parts and from theparts of the target polarized parallel to the polarization axis of thepart of the scanner, passes from one of the polarized parts of thescanner; while the optical radiation coming from those parts of thetarget polarized perpendicularly to the axis, does not pass or passes ina negligible quantity. Furthermore, the target may be projected ontoappropriated screens, like virtual or real screen(s), by means ofappropriate means.

For what concerns the image seen through the scanner, there are twoalternatives in which the polarized parts of the target are seen bycontrast with the background:

the polarized parts of the target are on a low luminance background, sothat the background and the polarized part(s) of the target withpolarization axis perpendicular to one of the polarized parts of thescanner, seen from the part of the scanner, have a similar luminance,such as to be not, or nearly not, distinguished due to lack or shortageof contrast between target and background, while the part(s) of thetarget with the polarization axis parallel to that of the part of thescanner are seen, through the part, light, i.e. bright, on a darkbackground, and may be distinguished from same. A similar process isdeserved for the other part of the scanner;

the polarized parts of the target are on a background with anappropriate luminance, sufficient for that the background and thepolarized part(s) of the target, with polarization axis parallel to theone of one of the polarized parts of the scanner, seen from the part ofthe scanner, have such a similar luminance that they can nearly not bedistinguished or can not be distinguished for lack or shortage ofcontrast between target and background, while the part(s) of the targetwith the polarization axis perpendicular to that of the part of thescanner are seen, through the part, dark on a light background, i.e.bright and distinguishable from the same. A similar process is deservedto the other part of the scanner.

The advantages according to the present invention are, beyond those dueto the provided use:

a reduction of the myopia progression due to accommodation and to theaccommodative system;

diagnostic action for anomalies of the accommodation and of theaccommodation system;

a therapeutic-rehabilitating action for the functional anomalies of theaccommodation and of the accommodative system;

reduction of the entity of the tonic accommodation;

the distancing of the remote accommodation point;

to initiate new studies linked to accommodation and to the accommodativesystem;

measuring of the accommodative power;

to be used in vision training procedure(s);

evaluation and measuring of the (possible) difference between exertedaccommodation and accommodative stimulus;

improvement of the efficiency of accommodation and of the accommodativesystem;

evaluation and measuring of the exerted accommodation;

the pointing out of latent hypermetropia, or of part of it;

the activation of psychi-physiological process(es) related toaccommodation and to the accommodation system.

The present invention will be described more in detail hereinbelowrelating to the enclosed drawings in which some embodiments are shown.

FIG. 1 shows a scheme of a system for the determination, the evaluationand the control of the refractive and accommodative, static and dynamicstatus of the eye, according to the present invention.

FIGS. 2, 3 and 3b show the details of a scanner and of a target, withpossibility of moving same.

FIG. 4 shows the formation of the images with the system according tothe present invention.

FIG. 5 shows an example of an image seen when the image of the targetgiven by the system according to the present invention lies before theretina.

The enclosed figures show one of the possible systems, according to thepresent invention, for the determination, the evaluation and the controlof the refractive and accommodative status of the eye, in which theoptical radiation coming from the part a of the target MR--polarized inparallel--passes through the part A of the scanner AN, and not throughthe part B of the same, as it is polarized in perpendicular with respectto the polarization axis of the same, and forms an image a'; in asimilar way the part b of the target forms an image b'.

When the power of the optic eye system varies, be the eye corrected ornot, and also the distance between the secondary principal plane P' andthe retina R, the image of the target may be:

before the retina R (in this case, the parts a' and b' of the image ofthe target on the retina appear moved to each other);

onto the retina R (in this case, the parts a' and b' of the image of thetarget onto the retina appear not moved to each other);

beyond the retina R (in this case, the parts a' and b' of the image ofthe target onto the retina appear moved to each other, and in a senseopposite to that described above).

The position of the image on the retina varies according to manyfactors, between which the most important are:

the distance between target and primary principal plane of the optic eyesystem, corrected or not;

ametropia of the eye;

eventual exerted accommodation;

eventual optic correction;

spectral composition of the luminance source(s);

possible aberrations, anisotropies, nonhomogeneities of the opticalmedia and of the eye.

The entity of the moving of the parts a' and b' of the image onto theretina of the parts a and b of the target MR, occurs according to thedistance from the retina at which the image of the target is formed,given by the optic eye system.

Relating in particular to FIGS. 2, 3, on the scanner AN and on thetarget MR are shown:

a half-field A of polarizing material;

an axis Y for the polarization of the half-field A;

a half-field B of polarizing material;

an axis X for the polarization of the half-field B;

a line S for separating the half-field A and the half-field B;

a part a of the target, of polarizing material;

an axis Y for polarizing a;

a part b of the target, of polarizing material;

an axis X for polarizing b;

a line S' for separating a and b.

It is possible to physically move a with respect to b (or b with respectto a) along a separation line, e.g. on an axis parallel to axis Y, asshown in FIG. 3B.

Furthermore, in FIG. 4 the following details are shown:

I=meeting point between visual axis and target

P=primary principal plane

P'=secondary principal plane

a₁ ' and b₁ '=images on the retina of a and b when I₁ ' (image of thetarget given by the optic eye system) is before the retina (I₁ 'P' RP')

a₂ ' and b₂ '=images on the retina of a and b when I₂ ' (image of thetarget given by the optic eye system) is on the retina (I₂ ' P'=RP') a₃' and b₃ '=images on the retina of a and b when I₃ ', (image of thetarget given by the optic eye system) is behind the retina (I₃ 'P' RP').

For what concerns the functioning of the system according to the presentinvention, if

the distance between target and primary principal plane of the optic eyesystem, corrected or not;

the possible optic correction;

the spectral composition of the luminance source(s), and

possible aberrations, anisotropies, nonhomogeneities of the opticalmedia and of the eye

are placed as fixed, and therefore as parameters, or are fixed, therefraction error of the eye and the possible exerted accommodationremain as variable elements, so that the refractive and/or accommodativestatus of the eye may be (subjectively) evaluated and the entity of theametropia and/or of the exerted accommodation may be measured, e.g.evaluating and measuring the apparent moving of the parts a' and b', inthe example physically moving the parts a and b of the target until thealignment of the parts a' and b' is reached (and thus restoring theshape of the target as if it was seen without the scanner); or placingbefore the eye a lens or lenses of such a power as to reach, as shown inthe example, the alignment of parts a' and b'.

If accommodation is exerted, it is possible to control if it is exertedin surplus, in the right entity or in shortage with respect to the onerequested for focusing at the distance at which the target is placed,furthermore allowing a retroactive voluntary control (by biofeedback) ofthe exerted accommodation, in the example evaluating the alignment ornot of the parts a' and b' of the target (and the possible variations ofthe position between a' and b'--or between b' and a'--in time).

The system according to the present invention includes a scanner(analyzer) and a target as shown in FIGS. 1 and 5. The analyzer isdivided in two semi-fields, perpendicularly polarized one to the other.The target is realized in such a way that from one polarized semi-fieldthe polarized part of the target with polarization axis parallel to saidpart of the analyzer can be seen (in the case of target with lightenedpolarized parts onto an opaque, dark background), or with thepolarization axis perpendicular to the one of the analyzer (and theperpendicularly polarized parts are seen dark on the lightenedbackground).

The target and its polarized parts may have many shapes and dimensions;in the enclosed figures, a simple target is shown, consisting only ofpolarized elements a and b.

The target MR is seen through parts A and B of the analyzer AN, with theeye optically adjusted or not; the image given by the optical system isformed before the retina, on the retina or beyond the retina, mainlyaccording to the distance of the target, to the refractivity device andto the relative location of a and b. If there is no adjustment andthrough the analyzer we look at the target, placed at the opticalinfinity, we will see α and β, which represent the projection into thespace of the retinal images a' and b' respectively of the polarizedparts a and b of the target; and these may appear;

aligned: in this case, the subject is emmetropic;

non aligned: in this case, the subject is ametropic.

The existence of nonalignment, which may be easily measured by means ofthe Vernier sharpness, is a direct function of the ametropy entity,i.e., the greater the nonalignment, the greater the ametropy; therelative position of α and β will be dependent on the polarization axisof the parts, on the polarization axis of the analyzer and on the kindof target, but however it will be in an opposite way in case of myopywith respect of the case of hypermetropia (in the example shown in thefigure, relating to a case of hypermetropia, part α appears to be higherthan part β6; the contrary occurs in case of myopy); conventionally, thedisplacement due to myopy is shown with a plus +, the one caused byhypermetropia with a minus -. The measuring and the optical compensationof ametropy may be performed as follows:

by placing before the eyes positive or negative lens such as to align αand β;

moving a with respect to b until the alignment with a and α is obtained,and measuring the entity of the adjustment (from the relation that linksthe apparent angular movement between α and β and ametropy). If anadjustment is performed, then the size of the adjustment will be addedto ametropy. Therefore, the present system has the function of asubjective refactometer, and may be used for determining the refractiveand the adjustment for any distance. Among the many possibleapplications of the present system, the most interesting concern:

measuring of ametropy (in case of astigmatism, target and analyzer arerotated);

balancing of the binocular vision (also in case of unilateral relativeamblyopia);

control of amending;

determining latent hypermetropia;

reduction of the amending component and of the subjective adjusting inmyopies;

valuation and control of the amending lag;

diagnosis and therapy of the amending anomalies;

valuation of the response of the visual system to the adjusting lens.

In possible variants of the system according to the present invention,the scanner according to above specification may be provided with adiaphragm D or not, may be rotated on the longitudinal axis LA (rotationmeans not shown) and may be linked or not to optical compensation OC andmay be part of other equipment.

In further variants, said target may have other structural elements(e.g. letters from the alphabet, gratings, etc;) so as to allow thecontrol of the focusing of the target, which in turn may be rotated (onthe longitudinal axis).

I claim:
 1. An optical system for use in evaluating an eye comprising:anilluminated target centered on and substantially perpendicular to alongitudinal axis extending from the eye to be examined, saidilluminated target includinga first polarized part with a substantiallyvertical polarizing axis, and a second polarized part with asubstantially horizontal polarizing axis, said second polarized part isadjacent to said first polarized part such that said first polarizedpart and said second polarized part slide relative to each other, and ascanner spaced from said illuminated target along the longitudinal axis,said scanner is substantially perpendicular to and divided about thelongitudinal axis intoa first half-field of polarizing material with asubstantially vertical polarizing axis, and a second half-field ofpolarizing material with a substantially horizontal polarizing axis; andwherein said illuminated target projects through said scanner onto theeye where parts of said illuminated target have a polarizing axis inalignment with half-fields of said scanner.
 2. The optical systemaccording to claim 1, further comprising a screen on which saidilluminated target is mounted, said screen is negligibly illuminatedsuch that a part of said illuminated target having a polarizing axisperpendicular to a half-field of said scanner matches the luminance ofsaid screen on the eye.
 3. The optical system according to claim 1,further comprising a screen on which said illuminated target is mounted,said screen is illuminated such that a part of said illuminated targethaving a polarizing axis parallel to a half-field of said scannermatches the luminance of said screen on the eye.
 4. The optical systemaccording to claim 1, further comprising a diaphragm centered about thelongitudinal axis and spaced between said screen and said illuminatedtarget.
 5. The optical system according to claim 1, further comprising arotation means to simultaneously rotate said illuminated target and saidscanner together about the longitudinal axis.
 6. The optical systemaccording to claim 1, further comprising an optic compensator centeredabout the longitudinal axis and spaced between said scanner and saidilluminated target.
 7. The optical system according to claim 1, whereinsaid illuminated target further includes means for controlling thefocusing of the eye.
 8. An optical system for use in evaluating an eyecomprising:a screen centered on and substantially perpendicular to alongitudinal axis extending from the eye to be examined, an illuminatedtarget spaced from said screen at an angle such that said illuminatedtarget projects on to said screen, said illuminated target includingafirst polarized part with a substantially vertical polarizing axis, anda second polarized part with a substantially horizontal polarizing axis,said second polarized part is adjacent to said first polarized part suchthat said first polarized part and said second polarized part sliderelative to each other, and a scanner spaced from said illuminatedtarget along the longitudinal axis, said scanner is substantiallyperpendicular to and divided about the longitudinal axis into a firsthalf-field of polarizing material with a substantially verticalpolarizing axis, and a second half-field of polarizing material with asubstantially horizontal polarizing axis; and wherein said illuminatedtarget projects through said scanner onto the eye where parts of saidilluminated target have a polarizing axis in alignment with half-fieldsof said scanner.
 9. The optical system according to claim 8, whereinsaid screen is negligibly illuminated such that a part of saidilluminated target having a polarizing axis perpendicular to ahalf-field of said scanner matches the luminance of said screen on theeye.
 10. The optical system according to claim 8, wherein said screen isilluminated such that a part of said illuminated target having apolarizing axis parallel to a half-field of said scanner matches theluminance of said screen on the eye.
 11. The optical system according toclaim 8, further comprising a diaphragm centered about the longitudinalaxis and spaced between said screen and said illuminated target.
 12. Theoptical system according to claim 8, further comprising a rotation meansto simultaneously rotate said scanner about the longitudinal axis andsaid illuminated target such that the projected image on said screenrotates in conjunction with the rotation of said scanner.
 13. Theoptical system according to claim 8, further comprising an opticcompensator centered about the longitudinal axis and spaced between saidscreen and said scanner.
 14. The optical system according to claim 8,wherein said illuminated target further includes means for controllingthe focusing of the eye.